The goals of this research project are to characterize the viariability between human lymphoid cell lines with respect to sensitivity to chemical mutagens, induction of gene mutations and the involvement of DNA-repair in modulating cell survival and mutation. Lymphoblasts cell lines and clones which are known to vary in sensitivity to chemical mutagens will be compared for differential ability to repair DNA damage as a function of dose, the specific mutagen employed and the time after mutagen treatment. Survivors of high doses or colonies obtained from biphasic portions of mutagen survival experiments will be characterized in a similar manner. Investigation of the variability in cell survival and mutation between normal lymphoid cells and cells from patients with xeroderma pigmentosum will be continued.